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Gli Ammassi Di Galassie

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Gli Ammassi Di Galassie Universo in Fiore 2017 CORSO BASE I GIGANTI DEL COSMO: GLI AMMASSI DI GALASSIE Sabrina De Grandi [email protected] Organizzazione spaziale delle galassie Ammassi Gruppi Galassie 100 mila a.l. ~30 kpc 3 milioni a.l. ~ 103 kpc 20 milioni a.l. ~ 7x103 kpc I primi cataloghi di ammassi Fino agli anni ’80: ispezione visuale di lastre fotografiche alla ricerca di sovradensita` di galassie. Es. di lastre fotografiche: • PSS: National Geographic Society-Palomar Observatory Sky Survey (Telescopio 5m Hale, Mt. Wilson US) • UKST: Schmidt telescope IIIa-J plates (Telescopio 1.2m, UK-Australia),… I cataloghi di Abell (1958) e Zwicky (1961-1968) Il catalogo piu` usato: Abell (1958) Emisfero Nord (2712) e A.C.O. (1989) Emisfero Sud (1364). 1958: Abell ispeziono` di 104 deg2 di lastre PSS (Luna ~0.25 deg2) Criteri principali: • almeno 30 galassie • compatto (0.02<z<0.2) • piano galattico escluso Dagli anni ’90: • algoritmi automatici di identificazione al posto dell’occhio umano. • Non più lastre fotografiche, ma immagini digitali (CCD) • SDSS (Sloan Digital Sky Survey), iniziata nel 2000 e tutt’ora in atto (35% del cielo osservato, 500 milioni di oggetti, catalogo di ammassi • Accesso libero ai dati (nel Telescopio dedicato ad 2015: 13o Data Release) Apache Point 2.5m (US) Immagine SDSS dell’ammasso A2142 MACS J1206.2-0847 DIAMETRO tipico di un ammasso di galassie ~ 20 milioni anni luce ~ 7 Mpc SPICA (훼 costellazione della Vergine) MACS J1206.2-0847 DIAMETRO tipico di un ammasso di galassie ~ 20 milioni anni luce ~ 7 Mpc ma… DISTANZA di MACS J1206 ~ 4.5 miliardi di anni luce ~ 1500 Mpc Dove si trova la Via Lattea in questa struttura universale? ovvero Noi ci troviamo in un Ammasso di galassie? Il Gruppo Locale 100.000 a.l. 1 Milione a.l. Il nostro vicinato NOI SIAMO QUI: VIA LATTEA Il Super-Ammasso di Virgo NOI SIAMO QUI 10 Milioni a.l. Il Super-Ammasso Locale NOI SIAMO QUI Nuova definizione del “Super-ammasso Locale” (basata sulla misura delle velocita` peculiari) COMA SHAPLEY Tully et al. 2014 Il GRANDE ATTRATTORE VIA LATTEA (punto focale gravitazionale) (al bordo di questa struttura enorme) PERSEUS-PISCES LANIAKEA Asse Maggiore = 520×106 ly (159 Mpc) 300-500 ammassi di galassie (2MASS survey) “Srotoliamo” la Volta Celeste Universo Locale (D < 200 Mpc) 2MASS (2 Micron All Sky Survey): osservate 1.6 milioni di galassie, rilevati centinaia (~500) di ammassi (Mt Hopkins, Arizona, Cerro Tololo Cile, 1997-2001) Qual’e` l’origine di Laniakea e di tutti i super-ammassi che vediamo nell’Universo vicino ? Partiamo da una mappa del cielo Mappa del cielo Mappa del cielo Mappa del cielo Mappa del cielo Mappa del cielo Radiazione di Fondo Cosmica (2.7K) Universo Primordiale Radiazione di Fondo Cosmica (2.7K) Universo Primordiale Radiazione di Fondo Cosmica (2.7K) Universo Primordiale Aumentando il contrasto fino a 1 parte su 100 mila si iniziano a vedere le anisotropie del fondo a microonde da cui si sono formate le strutture cosmiche Le variazioni della densita` locale oggi sono maggiori di quelle primordiali di molti ordini di grandezza! La sfida delle Cosmologia moderna: comprendere come le PICCOLISSIME anisotropie del fondo nelle microonde si sono potute trasformare nelle ENORMI strutture odierne cosmologia moderna Simulazione della formazione della Struttura su Grande Scala Gli Ammassi di Galassie si formano nei NODI dei filamenti cosmici e sono le strutture piu` grandi nell’Universo tenute legate dalla forza di gravita` DI COSA SONO FATTI GLI AMMASSI? AmmassoAmmassodidiGalassieGalassie: :nell’ottico nei raggi X Galassie: Fatte di stelle (gas/polvere). Visibili nell’ottico Telescopi a Terra e nello spazio KECK-USA: 2 da 10 metri VLT-ESO: 4 da 8 metri Hubble Space Telescope AmmassoAmmassodidiGalassieGalassie: :nell’ottico nei raggi X Ammasso di Galassie: nei raggi X Prima: fu la luce ….… e poi, tutto il resto dello spettro elettromagnetico In Astrofisica si usano le informazioni contenute in tutte le energie dello spettro elettromagnetico Astronomia X: l’assorbimento atmosferico Data di nascita dell’astronomia in banda X: 1962 con la scoperta della prima sorgente X (Scorpio X-1) Premio Nobel per la Fisica: 2002 a R. Giacconi Astronomia X: oggi Dal 1999, 2 grandi telescopi: XMM-Newton (ESA) e Chandra (NASA). Altri piccoli telescopi: Suzaku (JAXA), NuSTAR (NASA) A2199 A2029 A426-Perseus Proprieta` del Gas X degli ammassi: CALDISSIMO: T=10-100 milioni di gradi Proprieta` del Gas X degli ammassi: CALDISSIMO: T=10-100 milioni di gradi TENUISSIMO: densita` 0.1 atomi/cm3 Migliori Pompa a vuoto 100 atomi/cm3 Proprieta` del Gas X degli ammassi: TEMPERATURA: Atomo di Ferro 10-100 milioni di gradi DENSITA`: 0.1 atomi/cm3 COMPOSIZIONE CHIMICA: H, He con tracce di altri elementi non primordiali, es. Fe, Si, O, S,…. La composizione chimica del Gas X ci dice che: - Il gas e` stato processato nelle stelle (unica fornace nota) - Gli elementi sono stati prodotti da esplosioni di SN nelle galassie dell’ammasso - Devono esistere dei meccanismi di trasporto degli elementi chimici dalle galassie al gas caldo X - Meccanismi: venti stellari dalle galassie prodotti da SN, forze mareali/interazioni tra galassie, pressione d’ ariete… (esistono osservazioni di questi fenomeni) Di cosa sono fatti gli ammassi? Massa Galassie ~ 3% Di cosa sono fatti gli ammassi? Massa Galassie ~ 3% Gas intergalattico ~ 15% Di cosa sono fatti gli ammassi? Zwicky Zwicky (1934) Massa Galassie ~ 3% Gas intergalattico ~ 15% Materia Oscura ~ 82% 푀 푀 ~ 100-400 ⨀ 퐿 퐿⨀ Rubin Ammassi di Galassie : 2 grandi famiglie A478 (raggi X) COMA “Rilassati” “non-Rilassati” Ammassi di Galassie : 2 grandi famiglie A478 COMA “Rilassati” “non-Rilassati” Gli Ammassi di Galassie “Rilassati” Gli Ammassi di Galassie “Rilassati” raggi X ottico Abell 2029 – Galassia Centrale IC1101 (alone 6 milioni di al!) Gli Ammassi “rilassati” hanno (sempre) una galassia Ellittica gigante nel centro. BCG di Abell S740 M87 – BCG dell’Ammasso della Vergine NGC4696 – BCG dell’Ammasso del Centauro NGC 1275 – BCG dell’Ammasso del Perseo Come si formano le Galassie Centrali? Un caso di “cannibalismo”galattico Come si formano le Galassie Centrali? Un caso di “cannibalismo”galattico Sono le Galassie piu` luminose e massive dell’Universo Hanno aloni stellari estesissimi (milioni di anni-luce) Sono diverse dalle altre Galassie Ellittiche • hanno ancora tracce di formazione stellare • si trovano solo al centro degli ammassi • sono complesse (nuclei multipli, polvere, aloni..) … contengono i SMBH piu` grandi centrale Galassie Centrali degli Ammassi Massa del BH BH Massa del Massa del bulge della Galassia Hydra A: un ammasso “Rilassato” ottico raggi X XMM Cavita` nel gas caldo (osservato in X) Hydra-A Immagine composita: Chandra raggi X (blu) galassie (bianco), X (blu), radio (rosso) Cavita` nel gas caldo (osservato in X) MS0735.6+7421 HGC62 X (Chandra) Radio (VLA) X (Chandra) Radio 1’ = 200 kpc Perseo: l’ ammasso piu` brillante in X ottico Perseo: l’Ammasso piu` brillante in X XMM (raggi X) XMM Il centro dell’Ammasso del Perseo in X Chandra (raggi X) Osservazione Radio Osservazione X Cavita` X e Getti Radio sono prodotti da un Nucleo Galattico Attivo (AGN): la materia che “nutre” il SMBH induce potentissimi getti Attivita` dell’AGN centrale della galassia Centaurus A Getto Contro Getto SMBH Simulazione dell’ interazione tra un SMBH nella BCG (AGN) e il gas X dell’ammasso Onde sonore negli ammassi? L’espansione delle bolle puo` produrre onde sonore nel gas che trasportano l’energia prodotta dall’ AGN a tutto il gas Onde sonore SMBH Cavita` X Lenti Gravitazionali Lenti Gravitazionali 47 immagini multiple e almeno 12 galassie lontane distorte identificate A1689: ottico/X A1689: Ricostruzione di massa con lenti Le Masse Totali degli Ammassi misurate dall’ emissione X, dai moti delle galassie e dalle lenti gravitazionali sono consistenti tra loro (cioe` si trova la stessa quantita` di Materia Oscura). Ammassi di Galassie “non-Rilassati” raggi X cioe` ammassi di galassie in interazione Ammassi di Galassie “non-Rilassati” o meglio…… “Scontri tra Titani” Uno scontro molto particolare 1E 0657-156: Ammasso “Pallottola” Gas X Uno scontro molto particolare 1E 0657-156: Ammasso “Pallottola” “Pallottola”: è la parte di gas più interna e densa dell’ammasso che ha attraversato a velocita supersonica l’altro ammasso. SHOCK: prodotto da un’onda nel gas che si muove a velocità maggiore della velocità del suono. Quanta energia e` coinvolta in questa collisione? L’energia cinetica prodotta nello scontro e` pari a quella di circa 1050 bombe atomiche Shock Pallottola Turbulenza Sono gli eventi che producono piu` energia nell’ Universo dopo il BigBang 1E 0657-156: l’Ammasso “Pallottola” La “Smoking Gun” (prova provata) della Materia Oscura Galassie (ottico) 1E 0657-156: l’Ammasso “Pallottola” La “Smoking Gun” (prova provata) della Materia Oscura Galassie (ottico) + Gas (raggi X) 1E 0657-156: l’Ammasso “Pallottola” La “Smoking Gun” (prova provata) della Materia Oscura Galassie (OTTICO) + Materia Oscura (lenti gravitazionali) 1E 0657-156: l’Ammasso “Pallottola” La “Smoking Gun” (prova provata) della Materia Oscura Gas X Materia Oscura La collisione titanica ha separato la DM dalla materia ordinaria (gas atomico) 1E 0657-156: Ammasso “Pallottola” Simulazione conSimulazione materia oscura MACS J0025.4-1222: una altro esempio di collisione che ha separato la DM dalla materia ordinaria Gas (raggi X) Materia Oscura Galassie (OTTICO) A2744: Ammasso Pandora Immagine composita: Galassie, Gas X (rosso), DM (blu) Collisione tra almeno 4 ammassi Osservazioni nella
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